Underfeed stoker



Oct. 18, 1932. w. M. CROSS UNDERFEED STOKER Filed Jun 23, 1930 TORNEY BY f Patented Oct. 18, 1932 UNITED STATES PATENT lOFFICE WALTER M. CROSS, OF KANSAS CITY, MISSOURI, ASSIGNOR TO CROSS COAL-O-MATIC '.PANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF MISSOURI UNDERFEED STOKER Applicatongled June 23,

This invention relates to improvements in underfeed stokers, andrefers more particularly to a stoker which has provision for supplying air under pressure both to the combustion pot of the stoker and an auxiliary supplyvfrom the samesource to the tuyre grates surroundingV the combustionJ pot, which auxiliary air supply is normally at a lower pressure.

The invention further provides for the accumulation of slag or incombustible material around the combustion pot upon the tuyre grates by the positioning of the tuyre grates below the level of the upper edge of the combustion pot, preventing the flowing back of the molten or liquid slag into the throat of the combustion chamber.

This application is a continuation in part of a previous application, Serial 318,022, filed November 18, 1928.

Fig. 1 is a side elevational View of the stoker positioned in a furnace, with parts in section to disclose the operating mechanism.

Fig. 2 is a. view takenv along the line 2 2 in Fig. 1, looking in the direction of the arrow.

Fig. 3 is a modified type of combustion pot in which auxiliary air holes of predetermined size are used in place of the adjustable damper.

Referring to the drawing; a boiler 1, in which are flue tubes 2, is mounted within a furnace setting, the masonry in which is designated as 3. The combustion space in thc furnace 4 is available through a lire door 5. The stoker consists of a fuel hopper 6 and motor 7 driving a fan positioned within the casing 8. The fuel from the hopper is fed by moans o`f a screw 9 through the tube 10 into the combustion pot 11. Around the fuel tube is an air duct, designated as 12, to which air is' supplied under pressure by means of a fan 8, the air being discharged into the combustion pot through a plurality of tuyres 13 in the upper part of the combustion pot. Air supplied in this manner maintains the proper combustion conditions in combination with the fuel supplied from the hopper.

In the air duct 12, in a location beneath 1930. serial No. 463,212.

the combustion pot, is a port 14, closed by a damper 15. This damper is pivoted at 16 and is manipulated manually by means of a rod 17, which is fastened to the ldamper at the opposite end from the pivot point 16. By regulation of this damper by means of the rod 17, the auxiliary air which is released, from the duct l2 into the space 17 beneath the tuyre grates 18, is' positively regulated and controlled. J l

The function of the grates 18 which surround the combustion. pot is to support the burning fuel and slag discharged from the combustion pot during the operation of the stoker. Lugs or supports 19 are positioned e5 both on the combustion pot and on the side of the furnace setting at dierent heights so that the grates may be lowered or raised according to therequirements of operation.

In the operation of an underfeed Stoker 7a such as that shown, considerable difficulty has been experienced due to the draining of the g slag back into the combustion pot. This slag` accumulates in the bottom of the combustion pot or retort, an d hardens, at times interfering with the operation due to freezing of the screw 9 in the fuel tube 10. By lowering the tuyre grates 18 and furnishing space for the accumulation of the burning fuel, ash and l slag, this tendency for the slag to drain back se into the combustion pot has been entirely eliminated.

In practice, to assure proper operation over a burning period of 24 hours, the tuyre grates 18 are sufficiently depressed to permit 85 the accumulation of the slag for that period. The character of the coal usedwill determine the amount of slag accumulated within a given time, and there is provided, therefore, the adjustable arrangement of the grates. Tn other words, whenthe ash content or slag content in the fuel is high, the grates will be depressed considerably lower than when the ash content is low. With such coal as is available to the vicinity of western Missouri and eastern Kansas, depression of the grates 6 or 8 inches below the upper lip of the combustion pot has been found as a satisfactory position for the tuyre grates for operation over a period of 24 hours. An-

` tion of slag upon the tuyre grates.

other factor to be considered, of course, is the size of the furnace setting or the'square foot area available for the overflow material. ln the vertical portions of the grates as shown in my previous application are air ducts which permit the passage of the auxiliarly air through the material collecting upon the grates. During the operation oit the Stoker, the main draft is supplied to the combustion pot to the fuel burning therein, through the tuyres 13, while the auxiliary air supply spilling through the port 14 iurnishes air normally under lower pressure to the combustible material supported by the grates 18.

ln place of a damper as shown at 15 in Fig. l, there may be used a combustion pot such as shown in-Fig. 3, having air ports of a predetermined size. ln place of two ports, a single port may be used, or a plurality of ports of any configuration which will supply a predetermined amount of air tothe tuyre grates. rlhis air constitutes an auxiliary air supply corresponding to the air supplied through the duct 14 as shown in Fig. 1, thel opening of which air port is controllable by the damper.

As the slag and ash accumula-tes on the tuyre grates 18, the resistance to air going through the grates becomes relatively greater and the pressure in the retort or combustion pot and the air pressure supplied to the grates becomes more nearly-equalized. rlhis tendency toward equalization ofthepressure assures the proper airsupply to the tuyre grates and, consequently, the burning and consumption of any combustible vmaterial upon the grates. By having the air supplied from a common source as shown, the air draft supplied to the combustion pot and the air draft supplied to the tuyre grates, is controlled as to combustion requirements in the retort and onl the grates by the accumula- This slag reducing the size of the air ports through which air must pass through the tuyre grates, .reduces also the differential pressures maintained upon the retort and in the space under the tuyre grates'thus providing an automatic control of the air supplied to the grates and to the retort;

Underfeed stokers of this type, when used either for commercial or domestic use are at times rendered inoperable, particularly when p burning coal having an ash of relatively low melting point and Where the percentage of ash content in the lcoal is relatively high due t0 the draining 'back of the slag into the combustionl pot. the tuyre grates for the ash vaccumulation and positioning the grates lconsiderably below the rim of the retort, numerous service calls occasioned previously by clogging of the retort and screw with molten slag and ash have been eliminated.

Laeaaaa in the building. An outstanding advantage of the present arrangement is that no clinlrer or slag need be removed While the stolier is in operation, but instead the operator can clean the ash and clinkers out any time in the early morning when the lire box of the furnace is cold and the coal or combustible material burned from the ash which has accumulated on the tuyre grates.

Furthermore, during periods of ylight firing, the depressing of the tuyre grates below the rim of the retort permits the accumulation ofseveral days discharge from the retort without cleaning the material from the tuyre grates.

l claim as my invention:

1. ln an underfeed Stoker, a combustion pot, an air supply means surrounding the combustion pot, a plurality of vertically spaced lugs on said air supply means, an air chamber having Walls surrounding said air supply means, a plurality ofvertically spaced lugs on said walls, the lugs on vsaid air supply means and the lugs on said walls providing means for adjustably positioning said grates vertically below the combustion pot rim.

2. ln an underfeed Stoker, -a combustion pot, an air supply means surrounding the combustion pot, a plurality of vertically spaced lugs on said air supply means, an air chamber having walls surrounding said air supply means, a plurality of vertically spaced lugs on said Walls, the lugs on said air supply means and the lugs on said walls providing means for `adjustably positioning said grates vertically below the combustion pot rim, and means for bleeding air from said air supply means into said vair chamber.

3. In an underfeed Stoker, the combination including a lire box, a combustion pot positioned therein, grates surrounding said combustion pot, a plurality of vertically spaced supporting means positioned in said fire box to support said grates ,whereby said grates may be adjustably positioned below the rim of the combustion pot to permit the accumulation of unconsumed material on said grates and thus preclude it from clogging said combustion pot.

In testimony whereof I aix my signature.

yWALTER M. CROSS.

Since providing the space on 

